Re: [gentoo-user] 2GB of RAM

[Ralph Slooten]

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Thanks David for the clear answers.... I'll investigate further. As for
the rest of the PC.... running great with extra RAM ~ it's just UT2004 I
have discovered to have an issue here.

The 2/2 is what I'm running with at the moment ... seems to be fine.

Thanks again,
Ralph

David Klempner wrote:
> * Ralph Slooten <axllent@×××××.com> [2006-06-19 00:25]:
>> David Klempner wrote:
>>  > Note that without doing *anything*, with a normal 3G/1G split, you'll
>>> actually get 896M. Recent kernels added in a config option to have a
>>> 2.75G/1.25G split, which solves this problem; it makes sense to use that
>>> if you have 1G of RAM.
>> This option must be really new because I don't have it. I have two 3/1
>> options, a 2/2 option and a 1/3 option. Either way, I'm now using 2GB.
>
> It's one of the two "3/1" options; one of them is a PAGE_OFFSET of
> 0xC0000000 (3G) and the other is 0xB0000000 (2.75G); the latter is
> suggested for someone using 1GB. (I was making that change myself by
> hand until they added that option.)
>
> In fact, the 2G option is slightly lower than 2G, which is why it works
> with 2G of RAM.
>
>> Maybe this is the case, I'm not sure. For testing some other software I
>> upgraded to 2.16.6.16 2 weeks ago (when I still had 1GB) which resulted
>> in the same problem. I then went back to the previous-compiled 2.6.16.5
>> version which worked flawlessly. It is only now that I have actually
>> rebuilt the 2.6.16.5 kernel (due to RAM upgrade) and am having the same
>> problem. The NVidial kernel and glx (to be sure) were also rebuilt.
>>
>> I did a bit of testing last night before I went to bed and it seems that
>> no matter what options I use in the kernel I'm getting bad performance
>> now from the graphics card. It still gets > 4000 fps with glxgears
>> though, so I'm not 100% sure it is the graphics card.
>>
>> The question I was meaning to ask is what the ideal kernel settings
>> should be for 2GB of RAM... from there I'll look for other explanations
>> why the 3d isn't performing well.
>
> Do you have performance problems with any other applications? It
> wouldn't surprise me too much if it's some random library issue that
> specifically affects that game.
>
>> Should I use 2/2 *and* highmem, or just 2/2 ? You suggest the highmem
>> does very little, but it's there for a valid reason I take it.
>
> If you're doing 2/2, then don't bother with highmem. Without highmem,
> the kernel maps all of physical memory into its address space; this is
> naive and fast, but it means that normal processes don't get use of that
> space. This isn't a problem for most applications, but there are a few
> that expect the extra address space to be available. A direct result of
> the 2/2 split is that no single process can, even in theory, (directly)
> use more than 2G of RAM, because it can't even *address* more than 2G.
>
> This would be a more noticeable issue if you had 3G of RAM and did the
> 1/3 split; at that point, no process could use more than 1G. I've seen
> long running processes (for example, firefox after a month with several
> dozen open tabs) use more than that.
>
> Highmem adds an extra layer of indirection to solve this problem; it's
> slightly slower (but, I understand, the cost is minimal) but lets you
> have your address space back while still being able to use all of your
> RAM.
>
> My suggestion is to use 3/1 with highmem. If you want, you could also
> use 2/2 without highmem; it would probably be just slightly faster, but
> could break stuff. Using 2/2 with highmem is (I think) pointless.
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